Various types of batteries have been developed heretofore, and in every battery, a packaging material is an essential member for sealing battery elements such as an electrode and an electrolyte. Metallic packaging materials have often been used heretofore as battery packaging materials, but in recent years, batteries have been required to be diversified in shape and to be thinned and lightened with improvement of performance of electric cars, hybrid electric cars, personal computers, cameras, mobile phones and so on. However, metallic battery packaging materials that have often been heretofore used have the disadvantage that it is difficult to keep up with diversification in shape, and there is a limit on weight reduction.
Thus, a film-shaped laminate with a base material layer, an adhesive layer, a metal layer and a sealant layer laminated in this order has been proposed as a battery packaging material which is easily processed into diversified shapes and is capable of achieving thickness reduction and weight reduction (see, for example, Patent Document 1). The film-shaped battery packaging material is formed in such a manner that a battery element can be sealed by heat-welding the peripheral edge by heat sealing with the sealant layers facing each other.
The battery packaging material is molded with a mold at the time of enclosing a battery element, and is provided with a space for storing the battery element. During the molding, the battery packaging material is extended, so that cracks and pinholes are easily generated in a metal layer at a flange portion of the mold. As a method for solving this problem, a method is known in which the surface of a sealant layer of a battery packaging material is coated with an amide-based lubricant, or an amide-based lubricant is blended in a resin for forming a sealant layer, and bled out to the surface to improve the slippage of the sealant layer. When such a method is employed, the battery packaging material is easily drawn in the mold during molding, so that cracks and pinholes in the battery packaging material can be suppressed.
However, there is the problem that if the amount of an amide-based lubricant situated on the surface of the sealant layer is excessively large, the amide-based lubricant is deposited on the mold, and forms a lump to contaminate the mold. If other battery packaging material is molded using the contaminated mold, the lubricant lump deposited on the mold is deposited on the battery packaging material, and involved in heat-sealing of the sealant layer. Consequently, at the time of heat-sealing the sealant layer, the lubricant-deposited portion is unevenly melted, leading to occurrence of a sealing failure. For preventing such a situation, it is necessary to increase the frequency of cleaning for removing the lubricant deposited on the mold, so that the continuous productivity of batteries is deteriorated.
On the other hand, if the amount of the amide-based lubricant situated on the surface of the sealant layer is excessively small, the slippage of a battery packaging material is reduced, so that the moldability of the battery packaging material is deteriorated.